This invention relates generally to screw presses for expressing liquids from fibrous materials, and more particularly, to high pressure expressing presses capable of continuous operation, and to improved operating efficiency thereof.
Dewatering expressing presses are used on a variety of organic products to expel liquids from the fibrous solid material. In most cases, any remaining liquid must be removed through an evaporative drying process and the expenditure of considerable amounts of heat energy thereby. Examples requiring a secondary drying process are found in drying brewery spent grain, bagasse drying, waste solid concentration, and various vegatable oil extractions.
Screw presses used to express liquids from fibrous materials are well known in the industry. As prior art, applicant cites his earlier U.S. Pat. No. 4,440,076, and further prior art cited therein. Applicant's said prior patent was directed to improvements in efficiency derived from improved center drainage chamber design and screen bar placement. Other prior art known to applicant related to matters of efficiency in these screw presses are disclosed in U.S. Pat. No. 3,998,148 to Mainka, et al, and a U.S.S.R. Pat. No. 737,446.
One aspect of applicant's improvements in efficiency is derived from the particular construction of split-type worms and worm flights. In this regard, applicant further cites prior art in U.S. Pat. No. 3,980,013 to Bredeson which relates only generally to split, collared worm flights, and to similarly directed prior U.S. Pat. No. 635,868 to Peck.
The present invention discloses improved structure in the size and shape of screen bars in the collar surrounding the hollow main shaft, as well as those in the walls of the cylindrical main housing for improved liquid discharge from the compression chamber, as well as increased screen bar area available in the collar derived from improved split worm flight design. An improved method of operation relates to the intermittent introduction of compressed gas into the compression chamber during intermittent periods of compression relaxation. Further benefits derived from the improved screen bar design in the cylindrical outer walls relate to the elimination of otherwise necessary breaker bars, consequently reducing energy consumption. These improved screen bars are longitudinally and radially inwardly disposed from the main housing for eliminating spiraling of the fibrous material and for improved efficiency.